Nio and coo containing glass for television display cathode-ray tubes

ABSTRACT

A glass suitable for the window of a cathode-ray television display tube having a relatively increased transmission for red light (at approximately 618 mn) and a relatively decreased transmission for blue light (at approximately 455 nm). The glass, which is otherwise standard, includes NiO and CoO in a weight ration between 10 and 30 and satisfies the condition that

United States Patent Babcock .11.. 106/52 .LaGrouw 5] June 28, 1974 MDAND QQQCQNTAINING GLASSROR 3,143,683 8/1964 Duncan et a1. 106/52TELEVISION DISPLAY CATIIODERAY 3,222,206 12/1965 Cornelissen et al.106/52 TUBES 3,373,302 3/1968 Barber...1 106/52 1 3,416,937 12/1968Enomoto 106/54 [75 Inventor FOREIGN PATENTS OR APPLICATIONS 1,123,85781968 c; B 106 52 [73] Assignee: U.S. Philips Corporation, New mat mamYork, NY OTHER PUBLICATIONS Ceramic Industry Magazine, Glass Sands,(Sibia), [22] 1971 January 1967, pg. 138-139. [21] Appl. No.: 197,511

R I Primary Examiner-A. E. Curtis 63] C ed E S g gf f i 30 1969Assistant Examiner-Mark Bell 82 122 25 0 Attorney, Agent, orFirm-FrankR. Trifari [30] Foreign Application Priority Data [57] ABSTRACT July 3,1968 Netherlands 6809435 A glass Suitable for the Window of aCathode-ray television display tube having a relatively increased trans-52 us. (:1. 106/52, 106/47 R mission for red light approximately 618 anda 151 1111. C1. C03c 3/04, c03 3/24 relatively decreased transmissionfor blue light p- [58] Field 61 Search 106/52, 54, 47 R proximately 455The glass, which is Otherwise standard, includes N10 and C00 in a weightration be- 56] Ref en Ci tween 10 and 30 and satisfies the conditionthat UNITED STATES PATENTS 0.4 97C +21C O.5

z rg afi g C and (I representing the C00 and MO contents 2,991,1857/1961 Smith et a1 106/52 respect've 3,024,120 3/1962 2 Claims, 1Drawing Figure PATENTEDmza I974 llllllllllllllllllllllllllIIIIl A(nm)INVENTOR.

COENRAAD M. La GROUW NIO AND COO CONTAINING GLASS FOR TELEVISION DISPLAYCATHODE-RAY TUBES This is a continuation of application Ser. No.

837,794, filed June 30, 1969 now abandoned.

The invention relates to glass for an envelope of a cathode ray tube fortelevision display, particularly glass for the window of cathode raytubes for displaying coloured television images.

It is known to add a small quantity of two or more coloured oxides tothe screen glass for television display of both monochrome and colouredimages. These coloured oxides give the glass a substantially neutralgrey colour. its purpose is to mitigate the impeditive influence oflight sources outside the television set caused by reflection of lightfrom these sources against the luminescent layer and becoming noticeableby a reduction of the picture contrast. The action of these colouredoxides is based on the recognition of the fact that the light reflectedby the luminescent layer passes the glass of the window twice and thelight emitted by the luminescent layer passes the glass only once sothat the first-mentioned light is more attenuated than thelast-mentioned light.

The ratios between the quantities of nickel oxide and cobalt oxide,which are mostly used for this purpose, are chosen to be such that agiven overall transmission is obtained for the visible light. Inpractice, the weight ratio used between nickel oxide and cobalt oxide,lies at values between 2 and 9.

In the currently used luminescent substances the red luminescentsubstances have a smaller light output than the blue luminescentsubstances,

It is therefore necessary to ensure that the areas where the redluminescent phosphor is present on the screen are impinged upon byelectrons at a much greater energy than those where the blue luminescentphosphor is present. In practice this means that the electron gun, whichsupplies the electrons destined for the red phosphors, must be operatedat a voltage which is almost twice as high as that of the gun whichsupplies the electrons destined for the blue phosphors. This re-- ducesthe lifetime of the cathode ray tube rather considerably. The greenluminescent phosphors have a light output which is approximately theaverage of the red and the blue luminescent phosphors. In this respectthese do not therefore present any problem. The maximum values of theemission of the usual red, green and blue luminescent substanceslieapproximately at 618, 520 and 455 nm., respectively.

It is an object of the invention to increase the relative transmissionfor red of the glass of the window of the cathode ray tube relative tothe transmission for blue, the transmission for green remainingunchanged. As a result it is possible to reduce the required voltage ofthe electron gun supplying the electrons for the red luminescentphosphors to a considerable extent.

it has been found that this purpose is achieved by introducing in theglass a modification of the weight ratio between MO and C00.

According to the invention glass for an envelope of a cathode ray tubefor the display of television images, particularly display of colouredtelevision images and containing MO and C00 as colouredoxides, ischaracterized in that NiO and C00 are present in a weight ratio which isat least and at most while the condition is also satisfied, wherein Cand C represent the contents of these oxides in percent by weight in theglass.

The last-mentioned condition means that the overall transmission of theglass for. visible light relative to the known glass remainsapproximately the same. The two coefficients in the formula are thespecific absorption coefficients for the overall amount of visible lightfor the two coloured oxides.

The invention will further be described with reference to theaccompanying drawing, and a comparison of two glasses according to theinvention with a known glass. The drawing is a graphic representation ofthe transmission D in percent as a function of the frequency (cm) or ofthe wavelength (nm). Composition 1 is a known glass, the compositions 2and 3 are glasses according to the invention. The drawing shows that thetransmission for red (618 nm) of 2 and 3 relative to 1 is increased, thetransmission for blue (455 nm) is decreased while the transmission forgreen (5 20 nm) has remained substantially unchanged.

According to the invention any glass suitable for the display oftelevision images may be given an improved transmission"characteristicin practice.

Composition in by weight 1 M20, 3.4 3.4 3.4 Na O 9.0 9.0 9.0 K20 7.3 7.37.3 CaO L6 1.6 1.6 8:10 12.7 112.7 12.7 MgO 1.2 1.2 1.2 ceo, 0.2 0.2 0.2Sb O 0.6 0.6 0.6

CoO 0.0020 0.0013 0.0007 MO 00137 0.0150 0.0170

The use of glasses 2 and 3 for windows of colour television displaytubes has the result: that the gun supplying the electrons for the redphosphor can be operated at a voltage which is approximately 10 percentlower than when using glass 1.Lifet'ests have shown that as a 0.4 97cZIC 0.5

is satisfied, C and C representing the contents in percent by weight ofthe respective oxides C00 and NiO said weight ratio and condition beingsuch that said glass exhibits a transmission at 618 nm greater than at455 nm.

is increased from at least to at most 30 and where the condition 0.4 97CZIC 0.5 i

is satisfied, C and C representing the contents in percent by weight ofthe respective oxides C 41 and M0 and the glass has a composition inwelaht percent approximately as follows:

A1 0 3.4 sb o 0.6

Na O 9.0 C00 00013-00007 K20 7.3 NiO 00150-00170 CaO 1.6

BaO 12.7

MgO 12 said weight ratio and condition being such that said glassexhibits a transmission at 618 nm greater than at 455 nm.

mg I UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent N3821004 Dated June 28, 1974 Inventofls) VCOELIRAAD MARIA LA GROUW It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the title page in the abstract, line 3,

"(at a roximately 618 mn) should be -(at approximately 61.8 h Claim 2,line 14, after "C tiel line 14, reprint "and" in regular print Claim 2,line 1 of eolumn 4, "and glass has a composition in weight percentapproximately as follows: V

should be reprinted in regular print Signed and sealed this 3rd day ofDecember 197 4.

(SEAL) Attest:

riccormomsom JR. c. MARSHALL mm. Arresting Officer CoxmnissionerbfPatents

0.4<97CCOO+21CNIO<0.5
 2. In a glass of the type suitable for a window ofa cathode ray tube for the display of colored television images, theimprovement being that said glass consists essentially of cobalt andnickel, said glass having a relatively increased transmission atapproximately 618 nm and a relatively decreased transmission atapproximately 455 nm, said respective relative increase and decreaseoccurring as the weight ratio of NiO and CoO is increased from at least10 to at most 30 and where the condition 0.4 < 97CCoO + 21CNiO < 0.5 issatisfied, CCoO and CNiO representing the contents in percent by weightof the respective oxides CCoO 41 and NiO and the glass has a compositionin weight percent approximately as follows: